Thanks everyone for your replies. What I've gathered so far is:— The Sigma 50/1.4 is probably the sharpest at f/1.4 of the bunch, and nearly a match for the 50L's bokeh— The 50L has better build quality, weather sealing, bokeh and possibly microcontrast and color— The Sigma is prone to AF issues

I have the Sigma 35 and it's an excellent lens. It did take two copies to get a good one, though; the first front-focused badly.

I'm trying to decide whether the additional cost of the 50L is worth it. Sounds like I might be better off trying for a good copy of the Sigma 50 first.

I actually JUST had the Sigma 50mm f/1.4 delivered today. I already own the Canon 50mm f/1.4, but just never fell in love with it. I'm going to take some test shots on my 5Dm3 when I get home, and I'll post them here if anyone's interested. But there's been a slew of comparisons. I'm actually more curious to see how a new copy of the Sigma compares, as I've heard the newer copies of the 50mm fair better from an AF perspective.

I actually JUST had the Sigma 50mm f/1.4 delivered today. I already own the Canon 50mm f/1.4, but just never fell in love with it. I'm going to take some test shots on my 5Dm3 when I get home, and I'll post them here if anyone's interested. But there's been a slew of comparisons. I'm actually more curious to see how a new copy of the Sigma compares, as I've heard the newer copies of the 50mm fair better from an AF perspective.

If your body has it, I'd set AFMA for about a four foot subject distance @f/1.4. Then shoot something at about 40 feet @f/1.4. If it's way OOF at 40 feet, knowing what I know now about the issue, I'd say just send it to Sigma USA as long as you like what you see at 4 feet. They now have a very good fix for this issue in my experience and if you like what you see at 4 feet its probably a copy worth keeping imo.

Sure it stinks to send in a new lens and many people rail on Sigma about this, and I suppose rightfully so, but its not like Canon doesn't have issues with their 100L and apparently a bunch of them have worse focus issues than the Sigma 50...I know mine does. If you have an affected 100L it is purely a lottery each and every shot whether you get this weird softness that looks kinda like motion blur but not really the same. I know. I just spent $200 to have mine fixed because unlike Sigma's 3 year warranty, Canon only has 1 year. Still waiting to get it back from Canon to see if the $200 actually fixed this lightly used 14 mo old 100L that I paid extra to buy from an authorized dealer ... /rant off

If your body has it, I'd set AFMA for about a four foot subject distance @f/1.4. Then shoot something at about 40 feet @f/1.4. If it's way OOF at 40 feet, knowing what I know now about the issue, I'd say just send it to Sigma USA as long as you like what you see at 4 feet. They now have a very good fix for this issue in my experience and if you like what you see at 4 feet its probably a copy worth keeping imo.

The 50L needs to be used wide open, at f 2.0 - 2.8 the extra cost is for the bokeh. Also focus shift can be an issues at those f stops.

The 50L is awesome, but damn you pay for that little extra. Stopped down the 50/1.4 is 95%+ of the 50L. I have no experience wit the sigma 50.

That's the problem: I primarily want to use the 50mm from f1.4 to f/2.8. I have the 24-70 II and it is amazing at f/2.8 and 50mm, so there's not much point in me having a fast 50 if I can't use it wide open.

For me it was the opposite.I had both the Canon f1.4 and the sigma f1.4. I've done many tests both in the real world and test charts and maybe my Canon is a great copy but the sigma is anyways significantly less sharp when zoomed in.

I've already sent the sigma together with my body to sigma for calibrations twice, even did my own Focal calibrations at home and no matter what I do, the sigma can't hold up with the Canon.

Granted the sigma has much nicer bokeh but I'd rather it be sharper. In the end I sold the sigma

EvilTed

Just get a Sigma 35mm F/1.4, it's slightly wider but easier to use than the 50L and you can get really impressively sharp shots @ F/1.4, unlike the 50L @ F/1.2 which is a dreamy hazy look (you can always soften a sharp lens but not the other way around).

Thanks everyone for your replies. What I've gathered so far is:— The Sigma 50/1.4 is probably the sharpest at f/1.4 of the bunch, and nearly a match for the 50L's bokeh— The 50L has better build quality, weather sealing, bokeh and possibly microcontrast and color— The Sigma is prone to AF issues

I have the Sigma 35 and it's an excellent lens. It did take two copies to get a good one, though; the first front-focused badly.

I'm trying to decide whether the additional cost of the 50L is worth it. Sounds like I might be better off trying for a good copy of the Sigma 50 first.

IMO the L seems to have better contrast & more pleasing colors (how a lens can effect the colors is beyond me, but that's how it looks to me).

the Canon 50 1.4 looks like a good lens too, but I've read that the particular USM motor used in it is ancient & prone to breaking down. The 1.2L has the full time manual adjust high end USM motor, but because it's such a heavy lens focuses slightly slower than the 1.4. The sigma also seems to have more vignetting & chromatic aberration compared to the L from the reviews I have read.

the Canon 50 1.4 looks like a good lens too, but I've read that the particular USM motor used in it is ancient & prone to breaking down. The 1.2L has the full time manual adjust high end USM motor, but because it's such a heavy lens focuses slightly slower than the 1.4. The sigma also seems to have more vignetting & chromatic aberration compared to the L from the reviews I have read.

I broadly agree with the post but there are fact which are quoted wrong and need correction. The 1.4 also has full time manual focus and the reason why the 1.2L focuses slowly is because it is focuses by moving the lens elements in the front unlike the lens design for other USM lenses - not because it is heavy.

Then there's the Sigma 50/1.4. I've heard it might be the sharpest of all at f/1.4, but it's extremely prone to AF problems (which I'm not willing to deal with).

Not any more than other fast primes. When I tested mine against a stationary target it was more consistent in AF then Canon's 50 f/1.8 and 50 f/1.4, and just slightly less consistent then Canon's 85 f/1.8. It is on par with the L in terms of IQ and offers amazing bokeh, but is cheaper and lighter. I would recommend the Sigma out of all of them.